what advantages give having to engines in that position? wouldn't it be better twin engine (normal configuration) or single engine?

Compared to a regular twin-engine type, it has less drag, and you get an aircraft that's somewhat more compact and thus maneuverable.

Conversely, planes with this layout tend to be a bit cramped (two engines stuffed into the same size airframe as a single-engine plane) and they become dicey prospects to bail out of in case of damage.

Please enter the letters that are shown in the picture below (without spaces, and upper or lower case can be used). If you cannot identify the captcha even after reloading it please contact the administrator of this site.